Oxygen concentrator



FIG. 1 is a front elevation view of an oxygen concentrator showing the new design;

FIG. 2 is a back elevation view thereof;

FIG. 3 is a left-side view thereof;

FIG. 4 is a right-side view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a perspective view thereof; and,

FIG. 8 is another perspective view thereof.

The broken lines depict portions of the article that form no part of the claimed design. 

CLAIM The ornamental design for an oxygen concentrator, as shown and described. 